1. Field of the Invention
This invention relates in general to the field of transporting and controlling the temperature of integrated circuits ("ICs") and more particularly to an improved apparatus, system, and method of transporting ICs and controlling the temperature of ICs for testing.
2. Description of the Related Art
Previous systems for transporting IC devices to a test site use a carrier-conveyor system. The IC device is taken from a tray on which the IC device is resting in a "live bug" position (connections down) by a "pick and place" handling system. Typically, the pick and place handling system uses a vacuum handling device to pick up the IC device from its tray and place the IC device on a carrier, still in a live bug position. The carrier slides or moves through the conveyor towards the test site.
For testing at non-ambient temperature conditions, the carrier passes through or is contained within a passive convection heating or cooling apparatus, such as a convection oven or "soak site." The number of carriers in the conveyor, combined with the time spent at the test site, defines how long the convection apparatus is used to bring the IC device to the temperature desired for testing. A characterization process is typically used to determine whether the IC device has reached the desired test temperature by the time it reaches the test site. The characterization process usually requires the use of special thermal test devices with an external temperature measuring apparatus. The external temperature measuring apparatus may include thermocouple sensors which can read a thermocouple voltage and translate it into a temperature reading. Once the carrier reaches the test site, the IC device is typically removed from the carrier by a second vacuum handling device and is placed into a test site socket, with the necessary socketing force. In some systems, the IC device is not removed from the carrier. Instead, the carrier is placed under a contactor and the IC device is pressed against the test site socket, using a pressing mechanism. This approach is popular with memory IC handling systems or systems which achieve a high degree of parallel testing.
After testing, the IC device is placed back into the carrier by the vacuum handling device and the carrier continues to move through the conveyor system. In some systems, the conveyor system continues through a second convection apparatus, called a "de-soak chamber." The de-soak chamber is used to force the temperature of the IC device back to a safe handling temperature or above the dew point temperature.
That is, back to a safe handling temperature when the testing is hot, and above the dew point temperature when the testing is cold.
After exiting the de-soak chamber, if any, the vacuum handling device removes the IC device from the carrier and places it into a tray, typically a JEDEC (Joint Electronic Device Engineering Council) compliant tray. The particular tray used depends on whether the IC device successfully passed the testing process. Depending on the test results, the trays are dispatched to their next process location.
A disadvantage of such a system is that there is no provision to maintain the device under test ("DUT") temperature while the test is underway. Heat can be lost in some cases through the test site socket. The test can also cause the IC device to heat itself. For some critical, speed dependent tests, the resulting variation in the test temperature setpoint can frequently impair the quality of the test result.
Another disadvantage is that the complexity of and the number of moving parts of the soak and de-soak chambers can impair reliability of the handling system. Exposing moving parts, which may have different thermal expansion coefficients, to test temperatures complicates the design of the parts and subjects the operation to considerable wear. Passive convection heating and cooling apparatuses require that the moving parts of the apparatus be exposed to the sometimes extreme temperatures experienced by the IC device. These temperatures may affect the conveyor mechanism and further impair reliable operation. To remove an obstacle, clear a jam or service the system requires that the soak chamber be brought to safe handling temperatures. This consumes valuable production equipment utilization time. In the case of IC devices with a large thermal capacitance, the capacity requirements for the soak chamber are increased, which further aggravates the complexity and temperature exposure reliability concerns.
Therefore, a need has arisen for a system for transporting an IC device to a position for being tested which reduces the complexity of the transfer system. A further need exists for a system for transporting an IC device to a position for being tested which reduces the temperature exposure of the transport mechanism. A further need exists for a system which reduces the lost utilization time when the transport mechanism requires servicing. Another need exists for a system for efficiently bringing an IC device to a desired temperature for testing.